One of the responses I did not list was "anchor text" because I felt there was no way Google would turn off that factor, but a nice number of you, about 27, entered that in as "other" answer. Here are the responses to my poll:

I am honestly shocked so many people selected PageRank, but hey - the numbers do not lie.

Honestly, it is probably none of these factors. Bill Slawski listed his own theory on 12 factors that may have been turned off. Who knows? Only Google.